Currently, since a free-falling scheme is almost used when fluid is injected into a hospitalized patient, a nurse must frequently adjust the number of fluid drops which is varied with time after number of fluid drops is adjusted.
Conventionally, since the quantity of one drop is constant, it is possible to inject the exact quality of fluid through the dropping times of the fluid, so that this injection scheme has been used in hospitals until now.
As well known in the art, when the number of falls is 20 times, the quantity is 1 d. Thus, the injection quantity of 200 ml may be injected during two hours by suitably adjusting the number of falls.
However, the number of falls is dependent on a falling speed and the falling speed is generally dependent on the volume of a fluid pack or a hydraulic pressure varied with a position on which the fluid pack hangs, so a nurse generally adjusts the injected fluid by controlling an opening state of a medical fluid hose by using a clamp of a roller type installed to the medical fluid hose for injection (Korea Patent Patent No. 10-0813381).
However, when using the clamp, as the quantity of fluid reserved in the fluid pack is gradually reduced, the hydraulic pressure is reduced so that the number of falling is slow. Specifically, together with the above problem, if a nurse does not suitably adjust the quantity of fall for a suitable time period when an accurate injection of medical fluid is required, it is failed to suitably inject a quantity of medical fluid into a patient according to the prescription of a doctor so that a serious problem may be caused.
Thus, in recent, although an automatic injection apparatus capable of controlling a quantity of fluid has be developed and used, the automatic injection apparatus is very expensive since the automatic injection apparatus includes an injector and a controller as a set. In addition, in the state that the injection quantity is settled, the quantity of fluid may be changed according to the power current, so that it is difficult to achieve sufficient effect (Korean Patent No. 10-0530848, Korean Unexamined Patent Publication No. 10-2010-0027806).
Further, since the injection is performed to many patients in a hospital and the control of injection quantity is only dependent on nurse's personal exertions, it is very hard and difficult for the nurses caring many patients to adjust always and precisely the injection quantity.